A voltage-controlled oscillator (VCO) refers to a device that generates a desired frequency signal by altering a voltage applied from the outside, and is mainly used for wireless communication in analog sound mixing devices, mobile communication terminals, and the like.
FIG. 1A and FIG. 1B are circuit diagrams illustrating Colpitts voltage-controlled oscillators according to the related art.
A Colpitts voltage-controlled oscillator according to the related art, as illustrated in FIG. 1A and FIG. 1B, may be a PMOS Colpitts voltage-controlled oscillator (FIG. 1A) or an NMOS Colpitts voltage-controlled oscillator (FIG. 1B), each of which may include a MOS transistor Q, two capacitors C1, C2, an inductor L, and a current source IB for biasing.
A conventional Colpitts voltage-controlled oscillator may have cyclostationary statistic properties, and may have a low phase noise property due to its inherent resistance to flicker and thermal noises of active components.
However, the conventional Colpitts voltage-controlled oscillator may entail the drawback or requiring a relatively larger amount of current for generating the same negative Gm compared to a differential cross-coupled oscillator. Thus, there is a need for the development of a Colpitts voltage-controlled oscillator having improved power and phase noise properties.